Biology Paper 3 Marking Scheme - CATHOLIC DIOCESE OF KERICHO (CDK) EXAMS – 2018 PRE-MOCK WITH MARKING SCHEME

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BIOLOGY
PAPER 3
PRACTICAL
March 2018
MARKING SCHEME


CATHOLIC DIOCESE OF KERICHO (CDK) EXAMS – 2018
PRE-MOCK
BIOLOGY PAPER 3
MARKING SCHEME

INSTRUCTIONS TO CANDIDATES

  1. Answer all the three questions in the spaces provided
  2. You are required to spend the first 15 minutes of the 1 ¾ hours allowed for this paper reading the whole paper carefully before commencing your work.
  1.  
    1. Study the diagrams T1 and S1 carefully and answer the following questions:

      specimen 1 bio

      1. Name the parts labeled S2, S3, S4, S5 and S6. (5mks)
        S2 – Pericarp;
        S3 – Mesocarp;
        S4 – Seed;
        S5 – Endocarp;
        S6 – Fruit stalk;

      2. Name the parts labeled T2, T3, T4 and T5. (4mks)
        T2 – Remains of calyx;
        T3 – Placenta;
        T4 – Seed/ovule;
        T5 – Funicles;

      3. Complete the following table showing the type of fruit and reasons for each answer

        Specimen

        Type of fruit

        Reasons

        S1

        Drupe;

        - Once seed; Accept: hard or stony endocarp;

        Fleshy mesocarp; basal placentation

        T1

        Legume pod

        - Two sutures/two lines of weakness. Accept: marginal placentation.



      4. Complete the table below showing method of dispersal and reasons for each answer.

        Specimen

        Method of dispersal

        Reasons

        S1

        Animal

        - Bright colour; accept: fleshy mesocarp

        T1

        Mechanical (self-explosive mechanism

        - Two lines of weakness



    2. You are provided with a fruit labeled V.
      1. Cut a transverse section through specimen V. Draw and label of the cut surfaces. (4mks)

        cross section bio


      2. State the type of placentation of specimen V. (1mk)
        Axile;

      3. Squeeze out the juice from one of the halves of specimen V. Using the reagents provided carry out tests to identify the type of food substances present in the juice (3mks)

        Food substance

        Procedure

        Observation

        Conclusion

        Reducing sugar;

        - Add equal amount of Benedict’s soln. heat

        - Colour to orange/brown

        - Reducing sugars present

        Ascorbic acid or vitamin C

        - Add juice dropwise to DCPIP

        DCPIP discolourises

        Ascorbic acid or vit C. present




  2. Study the diagrams Q and R carefully and answer the following questions.

    specimen 2 bio

    1.  
      1. Name the phylum to which specimens R and Q belong. (1mk)
        Arthropoda

      2. State two reasons for your answer in a (i) above. (2mks)
        • Presence of exoskeleton;
        • have segmented body
    2.  
      1. Name the class to which each of R and Q belong (2mks)
        R - Insecta
        Q - Arachnida

      2. State reasons for your answer in (b) (i) above (2mks)
        R – three body regions; – three pairs of legs; One pair of antennae; One pair of compound eyes; One pair of spiracles per segment
        Q – Body divided into two parts (Cephalothorax and abdomen); Accept four pairs of walking legs

  3. Study the diagrams set A1, set E1, set M1 and set B carefully and answer the questions below

    specimen 3 bio

    1. State the conditions under which each set up was grown. (3mks)
      Set A1 – normal conditions
      Set E1 – in the dark
      Set B – unidirectional light

    2.  
      1. Name the phenomenon exhibited by seedlings in set E1 (1mk)
        Etiolation
      2. Give a reason why plants exhibit the phenomenon named in (b) (i) above (1mk)
        To reach light
    3.  
      1. Name the response exhibited by the seedlings in set B. (1mk)
        Positive phototropism
      2. Explain how the response named in (c) (i) above occurred (2mks)
        Auxins move to the darker side causing faster growth on this side; resulting in curvature of the shoot towards the source of light;
    4.  
      1. State the type of germination exhibited by seedlings in set A1 and set M1. (2mks)
        Set A1 – Epigeal;  Set M1 – hypogeal; 1mk

      2. Give a reason for your answer in (d) (i) above (2mks)
        Set A1 – cotyledons brought above the ground; Set M1 – cotyledons remain below the earth’s surface/underground;

 


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